If you have a old tired AH Sprite follow in the steps of a Sydney enthusiast and modify it to out accelerate an E-Type Jaguar.
IF, at traffic lights, you should happen to encounter a
bright red Mark One Sprite with four headlights and a fast-back hardtop,—don't
bother to challenge it unless you are operating something really potent.
Beneath that customised bonnet lurks a healthy Holden engine.
Now owned by Ken
Browning, the car was built by John Grant, who works at Penshurst Motors,
Sydney. He bought the Sprite from a wrecker after it had been written-off.
Before concerning himself with the mechanical side, John spent many weeks straightening
and realigning the monocoque structure. But before that was completed he began
thinking of fitting a Holden engine. After preliminary measuring he decided it
was feasible if the firewall and
surrounding panels were modified.
Normally the battery is mounted on a shelf on
the firewall which extends forward with the boxes that accommodate the
occupants' feet. The battery was re-located in the boot and the flat
panel removed back to where the firewall was vertical. The
inner sides of the boxes were then cut and rewelded so that they were parallel
to the car's centre-line, instead of angling in.
The modifications resulted in
a deep slot in the forward part of the body. This corresponds, in width, to the
sub-frame members. Extra bracing, in the shape of U-sections, was added to the
fire-wall at the top of, and between, the two boxes and also underneath the car
to act as another cross-member.
Some of the interior panelling had to be
altered too. The front of the driveshaft tunnel was extensively cut away to
make room for the gearbox—which sat further aft than originally. After the
engine and gearbox had been tentatively positioned, sheet metal was fabricated
and welded up to form a new gearbox cover.
Two 1 1/2 in SU carburettors, mounted on a log type manifold push fuel into the motor. One pancake type air filter does both units.
A stock Holden gearbox but with
floor-shift was retained. The cylinder block was bored out to 3 1/8th in—making
the capacity 2300 cc—and the cylinder head was thoroughly reworked with a
port-and-polish, larger valves, stronger springs and then planed to give 9 to 1
compression. Mery Waggott reground the camshaft and a pair of Myers cast-iron
exhaust headers were fitted with dual exhaust pipes merging to a single outlet.
John built the inlet system which has two 1z in SU carburettors on a log
manifold, but because there is very little room to spare beside the engine,
both carbs draw breath through a U-shaped manifold from one air cleaner.
A fantastic performer, the main problem with the Holden-Sprit is the handling. This will soon be improved by fitting wider rims on the rear wheels.
The
Sprite's radiator had been wrecked — it probably wouldn't have been big enough,
anyway —so a Vanguard cross-flow unit took its place. Even then some cooling
difficulties were
experienced until a Sprite top header tank was fitted and
the position of the filler neck changed.
The Sprite bonnet was also badly
damaged. While repairing it John thought he might as well go a bit further and
customise. The original headlights were discarded and their vacated locations
filled with sheet metal. The bonnet was then cut and L-section metal installed
to accept the dual Lucas set-up. Perspex covers were moulded to fit over the
lights and give as smooth a line as possible.
Unable to obtain Sprite seats at
a reasonable price, John installed those from a wrecked Minor 1000. The
interior was retrimmed and a console, housing three gauges and switches, was
built between the driveshaft tunnel and instrument panel. A wood-rimmed
alloy-spoked steering wheel replaced the original.
Driving impressions left no
doubt that this engine swap is far more successful than one would think.
Because the front of the Holden engine is no further forward than that of the
original 948 cc engine, the steering is little heavier than normal. Actually,
the extra weight is almost amidships and its affect is therefore minimised. The
wood-rimmed wheel gives the interior a sporting touch, and the stick-shift is
one of the best we have encountered. The pattern is the normal H-shape of a
conventional three-speed transmission. Its action is absolutely flawless; there
is not a fraction of lost movement and strong spring-loading against reverse allows
first-to-second changes that are most un-Holden-like. There is only about three
inches movement, at the knob, between any of the four positions.
Sever alterations had to be made to the firewall and transmission tunnel for the Sprite to accept the Holden motor.
The power and
the car's light weight mean that this Sprite is literally a top-gear-only
vehicle under most conditions. Although a four-speed box would provide slightly
better acceleration, John felt it wasn't worth the trouble and expense for a
car that serves primarily as a day-to-day hack. This is not altogther
surprising when you realise that the car has almost twice the power/weight
ratio of production Sprites. A stock Mark I Sprite weighs 12.75 cwt and has 43
bhp to do the work. The Holden-engined version weighs just under 14 cwt but has
at least twice the power. Assuming that the engine pumps out even a conservative
86 bhp, Ken's car has 6.14 bhp per cwt whereas the standard model has only 3.46
bhp per cwt.
 |
| The interior is extremely well finished. Gear shift is a delight to use. |
We were unable to obtain perfectly accurate acceleration times
because the rear axle had a Austin Lancer crown wheel and pinion fitted, and
the speedometer drive ratio had not been altered to compensate. However, by
pacing the Sprite against another vehicle we were able to mark the speedometer
so it was near-enough to correct.
Even if one takes a sceptical view, and adds another second or two to allow for wheelspin. the times are still very impressive. The engine winds up to 6000 rpm without hesitation in first and second gear, the speedometer showing 45 and 75 mph respectively. Foul weather prevented us from ascertaining the maximum speed but it must be in the vincinity of 110 mph!
As mentioned previously, the increased weight has not seemingly affected the Sprite's steering or handling. But the car's behavior was not all it could have been when we drove it—not quite up to Sprites' usual high standard. Over-size 5.90 tyres had been fitted to the rear wheels in an attempt to reduce wheelspin. And that they did —but at the expense of excessive tyre roll when cornering. The problem is due to be cured in either of two ways—by re-fitting standard-size tyres (and overlooking the wheelspin) or b-' adapting wider rims to the rear wheel centres.
We can't help feeling that this engine swap could well become popular throughout Australia. Early MkI Sprites are reasonably priced and Holden engines are certainly cheap enough. Off-hand we don't know of any other means as practical for obtaining so much performance for what should be a relatively modest sum.
SPORTS CAR WORLD, OCTOBER 1963
BY WAYNE ALLEN
